Almost a week after the release of the first beta, WordPress 4.9 Beta 2 was released yesterday for the general public to test.
The software is still in the development mode, and that is why it is best that you don’t run it on a production site. Consider setting up a test site just to play with the newest version. To get the taste of the future, WordPress 4.9, try the WordPress Beta Tester plugin (you’ll want “bleeding edge nightlies”). Or you can download the beta here (zip).
If you think you’ve found a bug, you can post to the Alpha/Beta area in the support forums. If you’re comfortable writing a reproducible bug report, file one on WordPress Trac, where you can also find a list of known bugs.